Snowmobiles are typically provided with a continuously variable transmission (CVT) to transmit power from the engine of the vehicle to the endless drive track, while changing the speed ratio between the engine and the endless drive track. Advantages of CVTs include smoother acceleration and improved fuel efficiency when compared to other types of transmissions.
Conventionally, snowmobiles have a pair of skis and an endless drive track for propelling the snowmobile, both of which are mounted to a frame of the snowmobile. The frame includes an engine compartment which conventionally has left and right sides, a bottom, a rear (bulkhead), and a front portion. The engine compartment supports power pack components such as an engine, an exhaust pipe, a muffler, a reduction gearing, and a CVT. The frame also includes a tunnel rearward of the engine compartment below which the endless drive track is disposed. The CVT has a driving pulley mounted to an output shaft of the engine, a driven pulley, and a belt looped around the two pulleys. The driven pulley is mounted to a countershaft and has a portion thereof which extends next to a side of the tunnel. The countershaft is operatively connected to the endless drive track so as to drive the endless drive track. U.S. Pat. No. 7,997,372, issued Aug. 16, 2011, the entirety of which is incorporated herein by reference, describes the above features of a snowmobile in more details.
The engine is usually mounted to the engine compartment through rubber mounts to reduce the transmission of vibrations from the engine to the frame. As a result, during operation, the engine moves relative to the frame. Therefore, the engine's output shaft, driving pulley and their common axis of rotation also move relative to the frame. The countershaft is rigidly supported near the engine compartment through bearings; as such its axis of rotation, which is also the axis of rotation of the driven pulley, does not move relative to the frame. As would be understood, this means that the axis of rotation of the driving pulley moves relative to the axis of rotation of the driven pulley. Therefore, the tension and alignment of the belt looped around the driving and driven pulleys changes due to these variations between the axes of rotation of the pulleys. This negatively affects the transfer of torque from the driving pulley to the driven pulley and may cause premature wear of the belt.
One possible solution to the above consists in mounting the engine to the engine compartment by using stiffer engine mounts. However, this results in more vibrations being transferred from the engine to the frame.
Therefore, there is a need for a snowmobile having a CVT mounting assembly which helps reduce the amount of vibration transferred to the frame.
There is also a need for a snowmobile having a CVT mounting assembly which reduces the variations in the distance between the driving and driven pulleys resulting from engine movement relative to the frame of the snowmobile.